I could just transfer my mind to an advanced cyborg body to gain any powers I want since I could customize it with all the DNA and tech I would want. shouldn't brainiac be absolute mind with his 12th level intellect?
Martian Manhunter is probably one of the most overpowered non-omnipotent superheroes in DC, at least to my knowledge. Shapeshifting, organic constructs, intangibility, telepathy, telekinesis, size alteration, unlimited duplication etc.
Martians in DC were so overpowered that the Guardians themselves had to instill a weakness to fire into the entire species, and even then, it's [usually] only psychological, meaning it can be overcome.